Unable to sysupgrade GL-Inet B1300 to Standard OpenWrt 18.06.0

I just got a new GL-Inet B1300. I'm trying to put the standard OpenWrt firmware on it.

When using the b1300 squashfs sysupgrade 18.06.0 file, I get:

sysupgrade -v -n /tmp/openwrt-ipq40xx-glinet_gl-b1300-squashfs-sysupgrade.bin 
error: mandatory section(s) missing from "/tmp/openwrt-ipq40xx-glinet_gl-b1300-squashfs-sysupgrade.bin". Abort...
Image check 'platform_check_image' failed.

From running dumpimage -l, it looks like there are two images, kernel and fdt. It looks like, however, sysupgrade wants a mandatory section that's in addition to those.

Does anyone know how to fix this problem?

Thanks!

Use U-Boot web recovery, but I highly recommend you to connect the router through Serial cable to determine the U-Boot version. The U-Boot version before April 2018 can't perform web recovery due to a bug.
You can also try U-Boot tftp (with or without Serial), but I haven't test this method yet.